Steam desuperheater



Aug. 26, 1930. I p VANDEVEER 1,774,114

swam DESUPERHEATER Filed Aug, 2, 1929 26 Jae/2%]? Patented Aug. 26, 1930 UNITED .STATES PATENT OFFICE PERRY O. VANDEVEER, OF WHITING, INDIANA, ASSIGNOR T STANDARD OIL COM- IANY, OF WRITING, INDIANA, A CORPORATION OF INDIANA STEAM DESUPERHEAT'ER Application filed August 2, 1929. Serial No. 383,100.

This invention relates to improvements in the method .of and apparatus for desuperheating steam and is more especially applicable to desuperheaters of the indirect or noncontact type.

In the art of steam power produotion, the

tendency has been to go to higher and higher pressures and greater degrees of superheat.

For example, it is now customary to produce superheated steam under-pressures in the nelghborhood of .400 pounds and at a temperature approximating 650 F. This steam is used largely in steam turbines and other power generating machinery, because of the increased efficiency obtained. When, however,.it is desired to use steam for heating purposes, oil distillation, and the like, it is disadvantageous to use steam of such a high Ordinarily for heat-- degree of superheat. ing purposes, boilers are operated to produce saturated steam; but in power plants, where it is desired to balance the operation of the plant by diverting superheated steam into the low pressure lines, it is advisable -to have a desuperheater which can be put into use at any particular time. My improved desuperheater and the method disclosed are designed to permit automatic desuperheating of steam under the conditions mentioned;

A desuperheater of a preferred type to which reference is made comprises primarily, a chamber for cooling the superheated or primary steam, a heat transfer medium, such as a coil, a water boiler in which new or secondarysteam is formed, and a connection for commingling the cooled superheated steam with the new or secondary steam from the .water boiler.

It should be understood that theterm desuperheated steam as used in this specification applies to steam which may be only partially desuperheated and not necessarily to steam with zero degrees of superheat.

. Among the features of my invention are the provision of a novel method and an appa- 7 ratus for controlling the rate of heat transfer and degree of desuperheating. Another feature of my apparatus is the provision of means whereby the water level in the boiler may becarried and maintained entirely above the tubes, if desired, thus lessening ebullition. and entrainment and maintainingmore uniforni temperature around the tubes and tube sheet, thus reducing strain and avoiding leaks.

My improved method and apparatus are I also deslgned to eliminate or reduce condensationin the primary steam passages.

By the use of my invention, the desuperheating of steam can be accurately controlled and efficiently carried on with a minimum of operating attention.

Heretofore, great difficulty has been encountered in controlling the amount of superheat removed from the steam. Attempts e5 have been made to do this by varying the level of the water surrounding the heat transfer tubes, but only a very erratic control could be obtained in this way. As the load on the apparatus varied, the amount of heat removed from the steam varied also. Since the heat transfer surface'is fixed in such type of apparatus, the rate of heat transfer must be varied with the load, but in prior systems of or apparatus for desuperheating there has, apparently, been little or no effective control on the rate of heat transfer underdifiering load and other conditions. Furthermore there has been no system or apparatus capable of maintaining a constant or a substantially s0 which is usually highly undesirable.

I have invented certain improvements in desuperheating apparatus by which the desuperheating operation is made practically automatic, and which will enable steam to be desuperheated over wide ranges of conditions with absolutely no attention to the apparatus '0 panying drawing in Vertical section.

, two sides of the As shown in the drawing, the apparatus includes a substantially cylindrical shell 10 with a divided primary steam chestll, 11 in the lower end, the two parts being separated by the vertical partition 16. Numeral 12 indicates a header lying above the steam chest. Above the header is a boiler or water chamber 13, and the space above this in the extreme upper part of the shell, as indicated by 14, constitutes the secondary steam chamber. Numerals 15, 15 indicate a plurality of hairpin or inverted U-tubesconnecting the steam chest 11 and 11 Numeral 17 indicates a combined water reservoir and steam separator adapted to reindicate a feed water pipe steam chest ceive steam from the shell 10 through the steam pipe 18 and supply water thereto through the water pipe 19. Numeral 20 may leading into the water reservoir 17.

Superheated steam may be supplied to the chamber 11 from the primary superheated, steam off valve 22. Such steam, after passing through the inverted U-tubes 15, where it gives up the desired amount of superheat to thewater 23 in the water chamber 13, enters the steam chest chamber 11, from which it leaves the apparatus through the pipes 24 and 26 controlled by the valves 25 and 50. The valve 50, passes the desuperheated steam into the low pressure line, which, for example, may lead to or be a part-of a low pressure plant distribution system, or the like.

Numeral 27 indicates the secondary steam ipe which conducts the secondary steam rom the apparatus to the line 26 where it mixes with the desuperheated primary steam.

Numeral 28 may indicate a by-pass controlled by the valve 29 for conducting superheated steam, as desired, directly to the plant distribution system or line 26. I shall assume that in the normal operation of the apparatus, the valve 29 remains closed.

Suitable pressure gages may be installed. Forv example, gages 30, 3,1, 32 and 33 may indicate the pressures, respectively, in the main superheated steam line, the primary steam chest chamber 11, the secondary steam chamber 14, and the plant distribution system 26.

line 21 through the shut .ing mist and ment is lessened by the use of my invention Numeral-34 indicates a regulating or relief valve, preferably of the automatic type, which can be set t6 maintain any desired pressure in the secondary steam chamber 14. Such valves are well known in the art and, consequently, the details and construction of the same need not be described here.

I have heretofore described my improved apparatus. This apparatus maybe operated in several ways. I shall now describe my improved method of desuperheating steam with this kind of apparatus. Superheated steam under high pressure is brought in through the line 21 and the valve 22. It is important to maintain an equal or a greater pressure on the secondary steam in the chamber 14 than on the primary steam in the tubes and primary steam chest 11, 11 This is accomplished by means of the regulating valve 34 which has heretofore been described, it being understood that this valve can be set to maintain in the chamber 14 a pressure higher than that in the primary steam chest I The higher the pressure maintained on the secondary steam in chamber 14, the hotter will be the water in the boiler, and the greater will be the degree of superheat retained by the primary steam. The valve 34 may be set for any degree of superheat. This greatly simplified operation isimportant when the apparatus is used as a balancing unit andrequired to operate over a wide range of capacity.

The water level 23 ably maintained above the tops of the tubes 1 15. Since no part of the tubes 15 is exposed,

entrainment of water in the secondary steam is reduced. Where heating tubes are allowed to extend vertically above the water level, there may be ebullition at the surface, producing spray which will be thrown on the hot projecting portions of the tubes, producentrainment. Such entrainwith the tubes submerged. By having the tubes completely submerged, there is also less strain put upon them and the header or tube sheet 12 with consequent less trouble from leaks. Of course, it should be understood that the apparatus is also operable with a "lower water level and exposed tubes.

By maintaining pressure in the secondary in the boiler is prefer- I steam chamber 14 and thus holding the water a 23 at an elevated temperature, a uniform operatlng condition can be obtained, as this LiU water, together with the Water 23 in the Water reservoir 17, will have approximately the same temperature as the stream which is being produced and it will act as a heat reservoir and a balance on the system.

Another advantage of operating the boiler under pressure is that the secondary steam is held in a denser form, thus reducing the actual volume of the steam which must be withdrawn from the boiler 14. This reduced volume aids in eliminating entrained water.

It will be apparent that the apparatus can be operated in other ways without departing from the spirit of my invention. Thus, if it is desired to produce steam at a temperature equal to or above the temperature of saturated steam the pressure of which corresponds to the pressure of the superheated steam in line 21. the apparatus can be controlled by valve 25, providing, of course, that the valve 34 is set to maintain a pressure on the secondary steam equal to or in excess of the pressure in the 'line 21 in order to avoid any condensation in the tubes 15. By operating in this way and maintaining a higher pressure on the primary steam in .the tubes 15, it should be possible to obtain 1 greater capacity from the apparatus because of the greater density of the steam in these tubes.

It is to be understood that feed water is introduced through the pipe 20 and that the water level 28 may be maintained by a suitable feed-water regulator 23". Any water .r that may be entrained in the secondary steam leaving the chamber'l is carried over into the separator 17 where it is separated from the steam, thus setting up a circulation which aids in the operation of the device. Obviously, the arrangement of the water reservoir and steam separating drum 17 might be altered in various Ways Without interfering with the operation of the apparatus. Thus, the drum might be placed horizontally or it might even be eliminated entirely under certain conditions.' g I also prefer to provide a valve 50, as shown, beyond the point where the secondary steam pipe 27 enters the low pressure line 26.

It will be seen that if the apparatus is controlled by this valve, the pressure in the secondary steam chamber cannot fall below the pressure in the primary steam chest 11, 11. This condition will be maintained bycontrolling the apparatus at the valve 50 even though the regulating valve 34 be omitted or left wide open. Of course, in the, event that it is desired to have a higher pressure in the secondary steam chamber than in the primary steamchest, this canbe accomplished by means of the regulating valve 34, above described.

Although I have shown and described certain forms of apparatus and certain methods, it is to be understood that variations in these the pressure of the secondary steam in the may be permitted without departing from the spirit of my invention; and that in the following claims it is my intention to claim all novelty in my invention relating to both apparatus and methods as broadly as possible, in view of the prior art.

What I regard as new, and desire to secure by Letters Patent, is:

1. A step in the method of operating a steam desuperheater of the indirect or noncontact type having a secondary steam chamber, comprising maintaining the pressure of the secondary steam in the secondary steam chamber substantially equal to or a predetermined amount above the pressure of the primary steam in the primary steam tubes.

type having a water container and a secondary steam chamber, including; maintaining a; secondary steam chamber substantially equal to or a predetermined amount above the pressure of the primary steam in the primary steam tubes, and maintaining the level of the water in the water container above the 100 tops of the steam tubes therein.

4. A steam desuperheater, including; a water container with a secondary steam chamber; primary steam tubes in the Water container; means for passing primar steam throughthe primary steam tubes; an means for automatically maintaining a predeter-. mined pressure in the secondary steam chamber substantially equal to or above the pressure of the primary steam in the primary 1m steam tubes.

5. A stepin the method of operatinga steam desuperheater ofthe indirect or non contact type consisting of automaticallymaintaining a predetermined pressure of the 1 1:, secondary steam in the secondar steam chamber substantially equal to or a ove the pressure of the primary steam in the primary steam tubes.

6. In a desuperheater, a primary steam 12o chamber, a secondary steam chamber, indirect heat transfer means between the primary and secondary steam chambers, means forv supplying water to ,the secondary steam chamber, and automatic means for maintain- 12a ing any desired predetermined pressure on the secondary steam chamber in excess of the pressure on the primary steam chamber.

7. In a desuperheater a primary steam chamber, a secondary steam chamber, indi 13a rect heat transfer means between the primary and secondary steam chambers, means for supplying water to the secondary steam chamber, automatic means for maintaining any desired predetermined pressure on the secondary'steam chamber in excess of the pressure on the primary steam chamber, and means for combining the steam from the secondary steam chamber and the primary steam chamber. 7

8. In a desuperheater, a primary steam chamber, a, secondary steam chamber, indirect heat transfer means between the primary and secondary steam' chambers, means for supplying water .to the secondary steam chamber, and automatic means for maintaining a constant pressure on the secondary steam chamber in excess of 'the pressure on the primary steam chamber 9. In a desuperheater, a primary steam chamber, a secondary steam chamber, a line for admitting superheated steam to the primary steam chamber, a valve in said line for controlling steam flow, a' delivery line leading from the primary steam chamber, a line connecting the secondary steam chamber and said delivery line, an automatic valve in said connecting line to maintain aconstant pressure on secondary steam chamber, and indirect heat transfer means between primary and secondary steam chambers.

10. An apparatus for reducing and controlling the degree of superheat in steam comprising, a primary steam chamber in heat exchange relation to a secondary steam chamber, means for supplying water to the secondary steam chamber, means for admitting superheated steam to the primary steam chamer, means for withdrawing partially desuperheated steam from the primary steam chamber to a discharging line, a conduit for withdrawing steam from the secondary steam chamber to said discharging line, and an automatic Valve placed in said conduit capable of maintaining a substantially-constant pressure in the secondary steam chamber. v

11. An apparatus for reducing and controlling the degree of superheat in steam comprising, a primary steam chamber in heat exchange relation to a secondary steam cham' ber; means for supplying water to the secondary steam chamber, means for admitting suerheated steam to the primary steam chamer, means for withdrawing partially desuperheated steam from the primary steam chamber to a discharging line; a conduit for withdrawing steam from the secondary steam chamber to said discharging line, and an au- ,tomatic valve placed in said conduit capable of maintaining a substantially constant pressure diiference between the secondary steam chamber and the discharging line.

. 12. A desuperheater comprising a water container having a secondary steam chamber, primary steam tubes in substantially fixed ma n;

position in said container, means for deliverlng primary steam into sald tubes, and means .for maintaining a predetermined pressure in the secondary steam chamber equal to or above the pressure of the primary steam in the primary steam tubes.

13. A desuperheater comprising a water container, water in said container, a secondary steam chamber communicating with said container for reception of steam therefrom, means for passing primary steam through said water out of direct contact therewith, and means for maintaining a constant pressure in said secondary steam chamber equal to or greater than the pressure on the primary steam supplied.

14:. A desuperheater comprising a water container, water in said container, a secondary steam chamber communicating with said container for reception of steam therefrom, means for passing primary steam through said water out of direct contact therewith, and means for maintaining a constant pressure in said secondary steam chamber greater than the pressure of the steam after passage through said water.

15. A desuperheater comprising a water container, water in said container, a secondary steam chamber communicating with said container for reception of steam therefrom, means for passing primary steam through said water out of direct contact therewith and means for maintaining a constant pressure difference between the pressure in said secondary'steam chamber and the pressure of the primary steam supplied, the pressure in said secondary chamber being equal to or above the pressure of the steam supplied.

16. A desuperheater comprising a water container,water in said container, a secondary steam chamber communicating with said container for reception of steam therefrom, means for passing primary steam through said water out, of direct contact therewith, and means for maintaining a constant pressure difference between the pressure in said secondary steam chamber and the pressure of the steam after passage through said water, the pressure in said secondary chamber being equal to or above the pressure of the steam supplied.

17. A desuperheater comprising a water container, water in said container, a secondary steam and water chamber communicating with said container for reception of steam therefrom and delivery of water thereto, means for passing primary steam through 'said water out of direct contact therewith,

means for maintaining a constant level of water in said secondary'chamber, and means for maintaining substantially constant the temperature of superheated steam passing from the desuperheater.

18. In a desuperheater of the indirect type, a water container, water in said container, a

' transferred from" the primary steam in said tubes.

secondary steam and Water chamber in com munication with said water container for reception of steam therefrom and delivery of water thereto, primary steam tubes in relatively fixed positionin said Water container, means for passin primary steam through said tubes, means for maintaining a constant level of water in said chamber, and means for said tubes for varying the amount of heat transferred from the primary steam in said tubes to said Water in accordance with a de sired characteristic of steam leaving said tubes.

20. In a desuperheater of the indirect type, a Water container, water in said container, a secondary steam and water chamber in communication with said water container for reception of steam therefrom and delivery of Water thereto, primary steam tubes in said Water container, means for passing steam that is to be desuperheated through said tubes means for maintaining a constant level of water in said chamber, and-means responsive to a characteristic of steam discharged from said tubes for'varying the amount of heat tubes to said water inaccordance with a desired characteristic of steam leaving sald 21 The method of desuperheating steam by an indirect or non-contact process, utilizing a heat exchanger having a water container and a chamber for steam generated from superheated 23. In a desuperheating system, a Water container,

passing superheated steam through said wa said water connected with said container,

taining said pressure at a desired difl'eren tial with respect to the pressure of the steam supplied to the desuperheater.

22. The method of desuperheating steam by an indirect or non-contact process, utilizter out of direct contact therewith, means for supplying water to said container in regulated quantity, and means'for maintalmng substantially constant the temperature of steam leaving said system solely by regulating the temperature of the water in said container. v 24. The method of operating a steam desuperheating apparatus of the indirect or non-contact type including a water container and a fixed steam passage therethrough, comprising, maintaining a substantially constant quantity of water in said container and maintaining said water at a substantially constant temperature.

In Witness whereof, I have hereunto set my hand this 26th day of July, 1929. i

- PERRY O. VANDEVEER.

comprising, maintaining pressure on the steam generated 1n sald container, and maining a heat exchanger having a water conf tainer and a chamber for steam generated connected with said contain- 7 from said water er, comprising, maintaining pressure on the steam generated in said container, and maintaining said pressure at a desired diflerem tial with respect to the pressure of the desteam.

water in said container, means for 

